Drainage water management effect on corn planting date in southeast Iowa

Abstract

In Iowa, producers achieve an adequate growing season for high yielding corn (Zea mays L.) by beginning field activities in a timely fashion. Subsurface drainage allows for early field activities by improving trafficability and decreasing excess water stress to crops on poorly drained soils. Drainage water management practices reduce drainage volumes and nitrate (NO₃) loss by maintaining the water table closer to the ground surface when compared to conventional drainage systems. The objective of this study was to determine the effect of shallow, controlled, conventional, and no drainage on depth to water table, volumetric water content, and soil temperature during a 51-day period, from mid-April through May, to evaluate if drainage water management practices delay planting. At the Iowa State University Southeast Research Farm near Crawfordsville, Iowa, we evaluated eight large-scale research plots with two replicates for each of the four drainage treatments over the 51-day planting period during 2012 to 2015. Each plot was planted half to soybeans (Glycine max [L.] Merr.) and the other half to corn, and the halves rotated every year in accordance with a typical corn–soybean rotation. Conventional and controlled drainage significantly lowered (p < 0.05) the water table when compared to the undrained treatment over the four-year study period. However, the shallow and undrained treatments significantly increased (p < 0.05) daily average soil temperatures at a 10 cm depth when compared to the conventional and controlled drainage treatments. Drainage treatment did not affect daily volumetric water content, maximum soil temperature, and minimum soil temperature at 10 cm. Overall, drainage treatment did not affect potential planting dates due to similar soil temperatures and volumetric water contents. However, drainage treatment does affect the depth of water table and reduces the risk of excess water stress on the crop during early season periods near planting.